Vatless additive manufacturing apparatus and method

ABSTRACT

An additive manufacturing apparatus includes: a build table, at least a portion of which is transparent, the build table defining a build surface; a material applicator operable to deposit a radio-energy-curable resin on the build surface; a stage positioned facing the build surface of the build table and configured to hold a one or more cured layers of the resin; one or more actuators operable to change the relative positions of the build table and the stage; a radiant energy apparatus positioned adjacent to the build table opposite to the stage, and operable to generate and project radiant energy on the resin through the build table in a predetermined pattern; a drive mechanism operable to move the build table so as to expose a new portion thereof for each layer; and material remover operable to remove remnants from the build surface. A method for using the apparatus is provided.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 15/802,351, filed Nov. 2, 2017, the content of which is herebyincorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

This invention relates generally to additive manufacturing, and moreparticularly to methods for curable material handling in additivemanufacturing.

Additive manufacturing is a process in which material is built uppiece-by-piece, line-by-line, or layer-by-layer to form a component.Stereolithography is a type of additive manufacturing process whichemploys a vat of liquid radiant-energy curable photopolymer “resin” anda curing energy source such as a laser. Similarly, DLP 3-D printingemploys a two-dimensional image projector, e.g. analog (masked lightsource) or digital (DLP or steerable mirror devices with light source),to build components one layer at a time. For each layer, the projectorflashes a radiation image of the cross-section of the component on thesurface of the liquid or through a transparent object which defines aconstrained surface of the resin. Exposure to the radiation cures andsolidifies the pattern in the resin and joins it to a previously-curedlayer.

In curing the photopolymer resin, it is preferable to have a freshsupply of material for each layer. Old resin may contain cured productssuch as supports that are broken off of the part or other externalcontamination. In a vat-based process, this contamination or thecontaminated material can cure into the component, resulting inundesirable geometry, or otherwise disrupt the build process and damagethe final part.

Another prior art method is a so-called “tape casting” process. In thisprocess, a resin is deposited onto a flexible radiotransparent tape thatis fed out from a supply reel. An upper plate lowers on to the resin,compressing it between the tape and the upper plate and defining a layerthickness. Radiant energy is used to cure the resin through theradiotransparent tape. Once the curing of the first layer is complete,the upper plate is retracted upwards, taking the cured material with it.The tape is then advanced to expose a fresh clean section, ready foradditional resin. One problem with tape casting is that it is wastefulbecause the tape is often not reusable.

BRIEF DESCRIPTION OF THE INVENTION

At least one of these problems is addressed by an additive manufacturingmethod in which material is deposited and cured on a rigid plate whichis moved to present a fresh surface between curing cycles.

According to one aspect of the technology described herein, an additivemanufacturing apparatus includes: a build table, at least a portion ofwhich is transparent, the build table defining a build surface; amaterial applicator operable to deposit a radio-energy-curable resin onthe build surface; a stage positioned facing the build surface of thebuild table and configured to hold a stacked arrangement of one or morecured layers of the resin; one or more actuators operable to change therelative positions of the build table and the stage; a radiant energyapparatus positioned adjacent to the build table opposite to the stage,and operable to generate and project radiant energy on the resin throughthe build table in a predetermined pattern; a drive mechanism operableto move the build table so as to expose a new portion thereof for eachlayer; and a material remover operable to remove remnants from the buildsurface.

According to another aspect of the technology described herein, anadditive manufacturing apparatus includes: a build table mounted forrotation about a central axis, wherein at least a portion of the buildtable is transparent, and build table defines a build surface; a drivemechanism configured to selectively rotate the build table about thecentral axis; a material applicator operable to deposit aradio-energy-curable resin on the build surface; a stage positionedfacing the build surface of the build table and configured to hold astacked arrangement of one or more cured layers of the resin; one ormore actuators operable to change the relative positions of the buildtable and the stage; a radiant energy apparatus positioned adjacent tothe build table opposite to the stage, and operable to generate andproject radiant energy on the resin through the build table in apredetermined pattern; a drive mechanism operable to move the buildtable so as to expose a new portion thereof for each layer; and amaterial remover operable to remove remnants from the build surface.

According to another aspect of the technology described herein, a methodfor producing a component layer-by-layer includes the steps of: applyinga radiant-energy radio-energy-curable resin on a build surface of abuild table which includes at least a portion which is transparent;positioning a stage at a predetermined distance from the build surfaceso as to define a layer increment in the resin; selectively curing theresin within a build zone on the build surface, using an application ofradiant energy in a specific pattern so as to define the geometry of across-sectional layer of the component; moving the build table and thestage relatively apart so as to separate the component from the buildsurface; advancing the build table so as to expose a new portionthereof; using a material remover to remove remnants from the buildsurface at a location downstream of the build zone; and repeating thesteps of applying, positioning, selectively curing, moving, advancing,and removing for a plurality of layers until the component is complete.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be best understood by reference to the followingdescription taken in conjunction with the accompanying drawing figuresin which:

FIG. 1 is a schematic side elevation view of an exemplary additivemanufacturing apparatus;

FIG. 2 is a schematic top plan view of the apparatus of FIG. 1;

FIG. 3 is an enlarged view of a portion of FIG. 1, showing a portion ofa material applicator of the apparatus;

FIG. 4 is a schematic side elevation view of an alternative materialremover;

FIG. 5 is a schematic top plan view of the material remover shown inFIG. 4;

FIG. 6 is a schematic side view of a beam scanning apparatus for usewith the apparatus of FIG. 1;

FIG. 7 is a top plan of the apparatus of FIG. 1, showing resin beingdeposited onto a build table thereof

FIG. 8 is a schematic perspective view of an exemplary materialapplicator suitable for use with the apparatus of FIG. 1;

FIG. 9 is a schematic top plan view of another alternative materialremover;

FIG. 10 is schematic side elevation view of an alternative additivemanufacturing apparatus;

FIG. 11 is a schematic top plan view of the apparatus of FIG. 10;

FIG. 12 is a schematic side elevation view of a stage and a vatcontaining cleaning fluid; and

FIG. 13 is a schematic side elevation view of a stage in an empty vatequipped with air nozzles.

DETAILED DESCRIPTION OF THE INVENTION

The concept disclosed herein presents an additive manufacturing methodand related apparatus in which curable material is deposited and curedon a generally stiff build surface that is spatially continuous beyondthe boundaries of a build zone where the curing takes place. Theapparatus is configured so as to move a clean portion of the buildsurface into the build zone when a particular curing cycle is completed.The method and apparatus include embodiments in which the materialdeposition and/or removal of excess uncured material is physicallydriven by movement of the build surface, and other embodiments in whichmaterial deposition and/or removal is carried out by independent means.

Referring to the drawings wherein identical reference numerals denotethe same elements throughout the various views, FIGS. 1 and 2 illustrateschematically an example of one type of suitable apparatus 10 forcarrying out an additive manufacturing method in which materialdeposition and/or removal is physically driven by movement of a buildtable. As will be explained in more detail below, it will be understoodthat other configurations of equipment may be used to carry out themethod described herein. Basic components of the exemplary apparatus 10include a build table 12, a stage 14, a material applicator 16, aradiant energy apparatus 18, and a material remover 20. Each of thesecomponents will be described in more detail below.

The build table 12 is a structure defining a planar build surface 22.For purposes of convenient description, the build surface 22 may beconsidered to be oriented parallel to an X-Y plane of the apparatus 10,and a direction perpendicular to the X-Y plane is denoted as aZ-direction (X, Y, and Z being three mutually perpendicular directions).

The build table 12 is sufficiently stiff such that, under the expectedloads applied during an additive manufacturing process, it does not bendor deflect enough to interfere with the additive manufacturing process,or cause an unacceptable amount of distortion or inaccuracy in thecomponent being produced. The desired stiffness may be provided througha combination of material properties (i.e. a sufficiently high modulus)and/or component design (i.e. thickness, stiffening features, etc.).

The build table 12, or selected portions of it, are transparent. As usedherein, “transparent” refers to a material which allows radiant energyof a selected wavelength to pass through. For example, as describedbelow, the radiant energy used for curing could be ultraviolet light orlaser light in the visible spectrum. Nonlimiting examples of transparentmaterials include polymers, glass, and crystalline minerals such assapphire or quartz. The build table 12 could be made up of two or moresubcomponents, some of which are transparent.

As illustrated, the build table 12 is disk-shaped to allow continuousmovement within the apparatus 10, as explained in more detail below.However, it should be appreciated that the build table 12 may defineother closed or open path shapes in other forms such as annular rings,straight lines, curves and/or polygons. Furthermore, these shapes mayinclude non-uniform features such as a varying width, or the inclusionof features (notches, slots, grooves, etc.) to facilitate locating oractuating the build table 12.

Means are provided for moving the build table 12 along a predeterminedpath. The path may be open or closed. For example, the path may be aline or an open or closed curve. In the illustrated example, the buildtable 12 is supported on a base 24 such that it can rotate about centralaxis 26. Support is provided by a plurality of support rollers 28between the base 24 and the build table 12. A drive mechanism isprovided in the form of a motor (such as an electric stepper motor) 30coupled to one or more of the support rollers 28. Other mounting anddrive systems are possible; the mounting and drive system would beselected as appropriate for the chosen build table shape and path shape.

The build surface 22 may be configured to be “non-stick”, that is,resistant to adhesion of cured resin. The non-stick properties may beembodied by a combination of variables such as the chemistry of thebuild table 12, its surface finish, and/or applied coatings. In oneexample, a permanent or semi-permanent non-stick coating may be applied.One nonlimiting example of a suitable coating is polytetrafluoroethylene(“PTFE”). In one example, all or a portion of the build surface 22 mayincorporate a controlled roughness or surface texture (e.g. protrusions,dimples, grooves, ridges, etc.) with nonstick properties. In oneexample, the build surface 22 may be overlaid with a flexible layer ofsilicone material. In one example, the build table 12 may be made froman oxygen-permeable material.

The apparatus defines a “build zone” 23 which is described in moredetail below. While only one build zone 23 is illustrated, it will beunderstood that multiple build zones may be provided, each with its ownassociated build apparatus such as the material applicator, materialremover, radiant energy apparatus, etc., as described below.

The stage 14 is a structure defining a planar upper surface 32 which isoriented parallel to the build surface 22.

Some means are provided for causing relative movement of the stage 14and the build table 12 relative to each other in the Z-direction. InFIG. 1, these means are depicted schematically as a simple actuator 33connected between the stage 14 and a stationary support structure 34,with the understanding devices such as pneumatic cylinders, hydrauliccylinders, ballscrew electric actuators, linear electric actuators, ordelta drives may be used for this purpose. In addition to or as analternative to making the stage 14 movable, the build table 12 could bemovable parallel to the Z-direction.

The material applicator 16 may be any device or combination of deviceswhich is operable to apply a layer of resin R over the build table 12and to level the resin R.

In the example shown in FIG. 1, the material applicator 16 includes ahollow tube 36 including a plurality of spaced-apart nozzle holes 38(see FIG. 3). In use, resin R optionally including a filler would bepumped into the interior of the tube 36 and discharged onto the buildsurface 22 through the nozzle holes 38 upstream of the build zone 23.

Means are provided for leveling the applied resin R. In the exampleshown in FIG. 1, the material applicator 16 includes a recoater 40 whichis a rigid, laterally-elongated structure positioned downstream of thetube 36. The recoater 40 is spaced a predetermined vertical distancefrom the build surface 22, thus defining a layer increment. This may berigidly fixed in place, or it may be connected to a separate actuator 42(FIG. 1) in order to enable a variable layer thickness. The actuator 42may be configured for purely vertical movement or may be configured forcontrolled tilting of the recoater 40 about one or more axes. In theillustrated example, the recoater 40 comprises a plurality of individualside-by-side sections 41, each with its own actuator 42. The height ofthe individual sections 41 may be varied as desired to producevariations in the layer thickness across the width of the build table12, or to compensate for variations in the layer thickness across thewidth of the build table 12.

The material remover 20 may be any device or combination of deviceswhich is effective to remove uncured resin R and other remnants from thebuild surface 22. Nonlimiting examples of suitable cleaning devicesinclude scrapers, brushes, suction or blowing mechanisms, absorbent orsponge-like devices, solvent rinsing equipment, or combinations thereof.

In the example shown in FIG. 1, the material remover 20 is configured asa scraper 44 which is a stiff, laterally-elongated structure. Thescraper 44 is static and functions by scraping material off the buildtable 12 and into a trough (described below), as the build table 12rotates underneath it. The scraper 44 may be oriented at an angle to theradial direction to encourage material to move radially off the buildtable 12. The scraper 44 may be coupled to an actuator 45 to permit itsheight or pressure against the build table 12 to be adjusted.Optionally, the scraper 44 may be made substantially wider than thematerial applicator 16, such that uncured material may be laid down andpicked up without any material flowing over the sides of the build table12. Depending on the properties of the build table 12, the materialremover 20 may instead be configured as a flexible squeegee-type deviceinstead of a stiff scraper.

Alternatively, the material remover could be an active device, with sometype of blade or other material-engaging element movable using one ormore actuators in a path causing the material-engaging element to movematerial off the build surface 22. For example, FIGS. 4 and 5 illustratea material remover 120 comprising a drum 122 mounted above the buildsurface 22 for rotation about a vertical axis 124. The drum 122 carriesa plurality of scraper blades 144 which are positioned to engage thebuild surface 22. In operation, the drum 122 would be rotated by a motor(not shown). As the drum 122 rotates, the scraper blades 144 wouldscrape uncured resin R off of the build table 12. This material wouldthen fall off the side of the build table 12 for disposal or recovery. Asqueegee 146 may be provided to scrape the material from the bottom edgeof the scraper blades 144 optionally, a blower (not shown may be used tohelp remove material from the scraper blades 144).

Referring back to FIGS. 1 and 2, a material circulating apparatus 46 maybe provided. In the illustrated example, this apparatus includes arecovery trough 48 positioned beneath the build table 12 and the scraper44. In operation, material scraped off the build surface 22 falls intothe trough 48. The trough 48 is connected to the material applicator 16by appropriate piping or another suitable conduit 50. A filter or screen52 may be provided to remove pieces of partially-cured resin R and otherremnants from the stream of material. A pumping element 54 may beprovided to move material through the circulating apparatus 46.Additionally, or as an alternative to the pumping element, one or moredevices such an auger 53 (here shown in the bottom of the trough 48) maybe used to move material in the apparatus. Augers may be especiallyhelpful for moving viscous material. New resin R and/or filler may beintroduced into the stream of material from a reservoir 56. Means may beprovided for mixing the resin R to ensure the material is homogenous(including for example, any or all of: new resin R, used resin R, newfiller, used filler). A schematic mixer 47 is shown in FIG. 1 which maybe used to mix or agitate the material before deposition.

The radiant energy apparatus 18 may comprise any device or combinationof devices operable to generate and project radiant energy on the resinR in a suitable pattern and with a suitable energy level and otheroperating characteristics to cure the resin R during the build process,described in more detail below.

In one exemplary embodiment as shown in FIG. 1, the radiant energyapparatus 18 may comprise a “projector” 58, used herein generally torefer to any device operable to generate a radiant energy patternedimage of suitable energy level and other operating characteristics tocure the resin R. As used herein, the term “patterned image” refers to aprojection of radiant energy comprising an array of individual pixels.Nonlimiting examples of patterned imaged devices include a DLP projectoror another digital micromirror device, a 2D array of LEDs, a 2D array oflasers, or optically addressed light valves. In the illustrated example,the projector 58 comprises a radiant energy source 60 such as a UV lamp,an image forming apparatus 62 operable to receive a source beam 64 fromthe radiant energy source 60 and generate a patterned image 66 to beprojected onto the surface of the resin R, and optionally focusingoptics 68, such as one or more lenses.

The radiant energy source 60 may comprise any device operable togenerate a beam of suitable energy level and frequency characteristicsto cure the resin R. In the illustrated example, the radiant energysource 60 comprises a UV flash lamp.

The image forming apparatus 62 may include one or morelight-manipulating elements such as mirrors, prisms, optical filters,splitters, optical fibers, photo-optical sensors, and/or lenses and isprovided with suitable actuators, and arranged so that the source beam64 from the radiant energy source 60 can be transformed into a pixelatedimage in an X-Y plane coincident with the surface of the resin R. In theillustrated example, the image forming apparatus 62 may be a digitalmicromirror device. For example, the projector 58 may be acommercially-available Digital Light Processing (“DLP”) projector.

As an option, the projector 58 may incorporate additional means such asactuators, mirrors, etc. configured to selectively move the imageforming apparatus 62 or other part of the projector 58, with the effectof rastering or shifting the location of the patterned image 66. Statedanother way, the patterned image may be moved away from a nominal orstarting location. This permits a single image forming apparatus 62 tocover a larger build area, for example. Means for mastering or shiftingthe patterned image from the image forming apparatus 62 are commerciallyavailable. This type of image projection may be referred to herein as a“tiled image”.

Alternatively, the radiant energy apparatus 18 may comprise a “scannedbeam apparatus” used herein to refer generally to refer to any deviceoperable to generate a radiant energy beam of suitable energy level andother operating characteristics to cure the resin R and to scan the beamover the surface of the resin R in a desired pattern. FIG. 6 shows anexample of a scanned beam apparatus 70 comprising a radiant energysource 72 and a beam steering apparatus 74.

The radiant energy source 72 may comprise any device operable togenerate a beam of suitable power and other operating characteristics tocure the resin R. Nonlimiting examples of suitable radiant energysources include lasers or electron beam guns.

The beam steering apparatus 74 may include one or more mirrors, prisms,and/or lenses and may be provided with suitable actuators, and arrangedso that a beam 76 from the radiant energy source 72 can be focused to adesired spot size and steered to a desired position in plane coincidentwith the surface of the resin R. The beam 76 may be referred to hereinas a “build beam”. Other types of scanned beam apparatus may be used.For example, scanned beam sources using multiple build beams are known,as are scanned beam sources in which the radiant energy source itself ismovable by way of one or more actuators.

The apparatus 10 may include a controller 78. The controller 78 in FIG.1 is a generalized representation of the hardware and software requiredto control the operation of the apparatus 10, including some or all ofthe material applicator 16, the stage 14, the radiant energy apparatus18, the material remover 20, and the various actuators described above.The controller 78 may be embodied, for example, by software running onone or more processors embodied in one or more devices such as aprogrammable logic controller (“PLC”) or a microcomputer. Suchprocessors may be coupled to sensors and operating components, forexample, through wired or wireless connections. The same processor orprocessors may be used to retrieve and analyze sensor data, forstatistical analysis, and for feedback control.

Optionally, the components of the apparatus 10 may be surrounded by ahousing 80, which may be used to provide a shielding or inert gasatmosphere using gas ports 82. Optionally, the housing 80 could betemperature and/or humidity controlled. Optionally, ventilation of thehousing 80 could be controlled based on factors such as a time interval,temperature, humidity, and/or chemical species concentration.

The resin R comprises a material which is radiant-energy curable andwhich is capable of adhering or binding together the filler (if used) inthe cured state. As used herein, the term “radiant-energy curable”refers to any material which solidifies in response to the applicationof radiant energy of a particular frequency and energy level. Forexample, the resin R may comprise a known type of photopolymer resincontaining photo-initiator compounds functioning to trigger apolymerization reaction, causing the resin to change from a liquid stateto a solid state. Alternatively, the resin R may comprise a materialwhich contains a solvent that may be evaporated out by the applicationof radiant energy. The uncured resin R may be provided in solid (e.g.granular) or liquid form.

Generally, the resin R should be flowable so that it can be leveledbetween the build table 12 and the build surface 22. A suitable resin Rwill be a material that is relatively thick, i.e. its viscosity shouldbe sufficient that it will not run off of the build table 12 during thecuring process. The composition of the resin R may be selected asdesired to suit a particular application. Mixtures of differentcompositions may be used.

The resin R may be selected to have the ability to out-gas or burn offduring further processing, such as a sintering process.

The resin R may incorporate a filler. The filler may be pre-mixed withresin R, then loaded into the material applicator 16. The fillercomprises particles, which are conventionally defined as “a very smallbit of matter”. The filler may comprise any material which is chemicallyand physically compatible with the selected resin R. The particles maybe regular or irregular in shape, may be uniform or non-uniform in size,and may have variable aspect ratios. For example, the particles may takethe form of powder, of small spheres or granules, or may be shaped likesmall rods or fibers.

The composition of the filler, including its chemistry andmicrostructure, may be selected as desired to suit a particularapplication. For example, the filler may be metallic, ceramic,polymeric, and/or organic. Mixtures of different compositions may beused.

The filler may be “fusible”, meaning it is capable of consolidation intoa mass upon via application of sufficient energy. For example,fusibility is a characteristic of many available polymeric, ceramic, andmetallic powders.

The proportion of filler to resin R may be selected to suit a particularapplication. Generally, any amount of filler may be used so long as thecombined material is capable of flowing and being leveled, and there issufficient resin R to hold together the particles of the filler in thecured state. The mixture of resin R and filler may be referred to as a“slurry”.

Examples of the operation of the apparatus 10 will now be described indetail. It will be understood that, as a precursor to producing acomponent and using the apparatus 10, the component 75 is softwaremodeled as a stack of planar layers arrayed along the Z-axis. Dependingon the type of curing method used, each layer may be divided into a gridof pixels. The actual component 75 may be modeled and/or manufactured asa stack of dozens or hundreds of layers. Suitable software modelingprocesses are known in the art.

Optionally, the build process may begin by applying a nonstick materialto the build surface 22 prior to resin application. For example, arelease agent such as polyvinyl alcohol (“PVA”) may be applied to thebuild surface 22 prior to each layer being built.

Optionally, to prevent sticking, some means could be provided to supplyoxygen through the thickness of the build table 12, in order to inhibitcuring of the resin R immediately adjacent the build surface 22 (oxygencan inhibit the curing of UV-curable resins).

The material applicator 16 is used to apply resin R to the build surface22. In the illustrated example, resin R flows out the nozzle holes 38and onto the build table 12. As the build table 12 rotates, it pulls theapplied material underneath the recoater 40 which levels the appliedmaterial to a desired thickness. The multiple sections 41 describedabove may be used to intentionally apply a layer having a varyingthickness across the width of the build surface 22, if desired.Alternatively, the multiple sections 41 (or the actuator 42 configuredto provide a pivoting movement) may be used to compensate for anyvariation from a desired uniform layer thickness. Such non-uniformitymight be caused by factors such as varying surface speed across thewidth of the build surface 22, variations in the resin viscosity, etc.This compensation could be carried out, for example, by positioning therecoater 40 at an acute angle (e.g. not parallel) to the build surface,so that the recoater 40 is closer to the build surface 22 at locationswhere variations would tend to produce an excessive resin layerthickness. The result would be a uniform layer thickness.

If excess material is applied, it is possible to provide one or moreside scrapers or additional catch troughs (not shown) to recover thematerial. This may then be drained or pumped away, or removed manually.

Optionally to reduce the chance of applying excess material, the widthof the resin layer which is applied may be substantially narrower thanthe build table 12, so that there is a lateral margin on each side andno material flows over the sides. For example, as shown in FIG. 7, thewidth of the band of resin R is narrower than the build table 12.

Depending on the specific application, it is possible that there will beeither an excess build up or an inconsistent layer during a transition,i.e. when the motion of the build table 12 starts or stops. If suchtransitions areas are present, it would be helpful for part uniformitythat the build zone 23 not coincide with these transition areas. Thesize of the transition areas (if present) is likely to be fairlyconstant. It is possible to avoid these transition areas either bymaking the minimum advance of the build table 12 (i.e. number of degreesrotated) greater than the size of the transition area plus the size ofthe desired build zone 23 for one component, or to rotate the buildtable 12 a relatively large amount between layers, providing a largezone that is guaranteed to have a uniform slurry height. To avoid wasteof material in this case, it is possible to manufacture severalclosely-spaced components in the zone between the material applicator 16and the material remover 20.

Optionally, different layers may comprise two or more different materialcombinations of resin R and/or filler. As used herein, the term“combination” refers to any difference in either of the constituents.So, for example, a particular resin composition mixed with two differentfiller compositions would represent two different material combinations.For example, one layer may comprise a first combination of resin R andfiller, and a second layer may comprise a different combination of resinR and filler. The different materials may be provided, for example, byproviding one or more additional supply containers 156, as seen in FIG.1.

After the material is deposited, the apparatus 10 is positioned todefine a selected layer increment. The layer increment is defined bysome combination of the thickness that the resin R is applied by thematerial applicator 16 and the operation of the stage 14. For example,the stage 14 could be positioned such that the upper surface 32 is justtouching the applied resin R, or the stage 14 could be used to compressand displace the resin R to positively define the layer increment. Thelayer increment affects the speed of the additive manufacturing processand the resolution of the component 75. The layer increment can bevariable, with a larger layer increment being used to speed the processin portions of a component 75 not requiring high accuracy, and a smallerlayer increment being used where higher accuracy is required, at theexpense of process speed.

Once the resin R with filler has been applied and the layer incrementdefined, the radiant energy apparatus 18 is used to cure atwo-dimensional cross-section or layer of the component 75 being built.

Where a projector 58 is used, the projector 58 projects a patternedimage 66 representative of the cross-section of the component 75 throughthe build table 12 to the resin R. Exposure to the radiant energy curesand solidifies the pattern in the resin R. This type of curing isreferred to herein as “selective” curing.

Once curing of the first layer is complete, the stage 14 is separatedfrom the build table 12, for example by raising the stage 14 using theactuator 33.

Optionally, the component 75 and/or the stage 14 may be cleaned toremove uncured resin R, debris, or contaminants between curing cycles.The cleaning process may be used for the purpose of removing resin Rthat did not cure or resin R that did not cure enough to gel during theselective curing step described above. For example, it might be desiredto clean the component 75 and/or the stage 14 to ensure that noadditional material or material contamination is present in the finalcomponent 75. For example, cleaning could be done by contacting thecomponent 75 and/or the stage 14 with a cleaning fluid such as a liquiddetergent or solvent. FIG. 12 shows one example of how this could beaccomplished by providing a cleaning vat 391 containing the cleaningfluid. The cleaning vat 391 comprises a floor surrounded by a peripheralwall. In use, the cleaning fluid 97 would be placed in the cleaning vat391. A suitable mechanism (not shown) would be used to move the cleaningvat 391 into position under the stage 14. The stage 14 would then belowered to bring the component 75 into contact with the cleaning fluid97. Upon completion of the cleaning cycle, the stage 14 would then beraised to move the component 75 clear of the cleaning vat 391. FIG. 12illustrates several different possible means for producing this relativemotion. As one example, a mechanical mixing blade 392 may be used toagitate the cleaning fluid 97. As another example, an ultrasonictransducer 394 coupled to the cleaning vat 391 may be used to produceultrasonic waves in the cleaning fluid 97. As another example, one ormore nozzles 396 may be used to introduce jets of flowing cleaning fluid97. As yet another example, appropriate actuators (not shown) may beused to produce relative motion of the stage 14 and the cleaning vat391. Optionally, the cleaning process may include a “drying” step inwhich the freshly cleaned component 75 is positioned within an emptycleaning vat 491 (FIG. 13) with air nozzles 492 which would be used todirect jets of air at the component 75 for the purpose of blowing off orevaporating the cleaning fluid. Depending on the particularcircumstances, the “drying” step may be sufficient to clean thecomponent 75 in and of itself. Subsequent to the cleaning step, thecleaning vat would be moved away from the stage 14.

The build table 12 is then advanced to move the build surface 22 underthe material remover 20, thus removing any excess cured or uncured resinR, filler, release agent, or other remnants. The excess uncured resin Rand filler flows into the catch trough 48 and is recycled as describedabove.

Concurrent with the step of removing or cleaning remnants from the buildsurface 22, additional resin R with filler is applied to the cleanportion of the build surface 22, which is exposed by rotation of thebuild table 12. Another layer increment is defined, and the projector 58again projects a patterned image 66. Exposure to the radiant energyselectively cures resin R as described above, and joins the new layer tothe previously-cured layer above. This cycle of applying resin R,incrementing a layer, and then selectively curing is repeated until theentire component 75 is complete.

Where a scanned beam apparatus is used instead of a projector, the buildprocess is similar except for the curing step. To carry out the curing,the radiant energy source 68 emits a beam 66 and the beam steeringapparatus 70 is used to cure the resin R by steering a focal spot of thebuild beam 66 over the exposed resin R in an appropriate pattern.

Either curing method (projector or scanned) results in a component 75 inwhich the filler (if used) is held in a solid shape by the cured resinR. This component may be usable as an end product for some conditions.Subsequent to the curing step, the component 75 may be removed from thestage 14.

If the end product is intended to be purely ceramic or metallic, thecomponent 75 may be treated to a conventional sintering process to burnout the resin R and to consolidate the ceramic or metallic particles.Optionally, a known infiltration process may be carried out during orafter the sintering process, in order to fill voids in the componentwith a material having a lower melting temperature than the filler. Theinfiltration process improves component physical properties.

In the method described above, the material application and the materialremoval are physically linked to, and driven by, the movement of thebuild table 12. Alternatively, an additive manufacturing method may becarried out in which the material application and/or the materialremoval are independent of movement of the build table 12. Thisalternative method may be carried out using the apparatus 10, orsuitable modifications thereof.

For example, a material applicator which does not require build tablemovement may be substituted for the material applicator 16. FIG. 8illustrates an example of a suitable type of material applicator 216comprising a supply container 236 with a nozzle 238 and a flow controlmechanism 240. Appropriate means are provided for controlled 3D movementof the material applicator 216 over the build surface 22 (e.g. in X, Y,Z axes). FIG. 12 shows an actuator assembly 241 as an example. This typeof material applicator 216 is capable of depositing resin R in layershaving arbitrary shapes and variable thickness. In the example shown inFIG. 8, an exemplary layer 180 has some areas (exemplified by section182) having a relatively smaller thickness and other areas (exemplifiedby section 184) having relatively larger thickness. The layer 180 mayalso include areas devoid of material (exemplified by open area 186).The shape of the various sections of layer may be arbitrary, asexemplified by the raised section 184.

Nonlimiting examples of other suitable resin application devices that donot require build table rotation include chutes, hoppers, pumps, spraynozzles, spray bars, or printheads (e.g. inkjets).

Once the resin is applied to the build surface 22, the apparatus 10 isused to carry out the build step described above, including positioningto define a selected layer increment, using the radiant energy apparatusto cure a two-dimensional cross-section or layer of the component 75being built, and separating the stage from the build table 12.

The build table 12 is then advanced to move a new, clean portion of thebuild surface 22 into the build zone 23, thus readying the apparatus fora subsequent layer.

Concurrently or subsequently to advancing the build table 12, a materialremover is used to remove any excess cured or uncured resin R, filler,release agent, or other remnants from the build surface 22. It will beunderstood that the material remover can be located anywhere in theapparatus 10 downstream of the build zone 23.

To carry out this step, a material remover may be provided which is notdependent upon movement of the build table 12. For example, the materialremover 120 described above and shown in FIG. 5 could be used. As analternative, FIG. 9 illustrates a material remover 320 comprising ablade 344 resting on the build surface 22 of the build table 12 andoriented for movement in a radial direction. An actuator 346 is providedto provide alternate retraction and extension along the axis of thearrow in the figure. This movement would be used to scrape uncured resinand other remnants from the inner radius of the build table 12 to theouter radius and then off into the trough as described above.

FIGS. 10 and 11 illustrate schematically an alternative additivemanufacturing apparatus 510. The apparatus 510 is similar in overallconstruction to the apparatus 10 described above. Elements notseparately described may be considered to be identical to the apparatus10. The apparatus 510 includes a build table 512, a stage 514, amaterial applicator 516, a radiant energy apparatus 518, and a materialremover 520.

The structure and operation of the apparatus 510 are substantiallysimilar to the apparatus 10 described above, with the primary differencebeing that the movement used to advance the build table 512 betweenbuild cycles is linear rather than rotational.

As illustrated, the build table 512 is generally rectangular. Othershapes defined by lines, curves and/or polygons may be used.Furthermore, these shapes may include non-uniform features such as avarying width, or the inclusion of features (notches, slots, grooves,etc.) to facilitate locating or actuating the build table 12. Theoverall width “W” and the overall length “L” may be selected to suit aparticular application. Means are provided for moving the build table512 along a predetermined path such as line or an open curve (either ofthese may be considered an “open path” as opposed to a “closed path”).In the illustrated example, the build table 512 is supported on a base524 by a plurality of support rollers 528. One or more of the supportrollers 528 may be motorized. Other mounting and drive systems arepossible. The drive system is operable to move the build table 512through the apparatus, for example from left to right as shown by thearrow in FIG. 10.

Other than the table advance motion, operation of the apparatus 510 tobuild a component 75 is substantially the same as for the apparatus 10described above. In particular, any or all of the options for applyingmaterial and/or removing material as described above may be implementedin the apparatus 510. That is, material application and/or materialremoval may be linked to movement of the build table 512, or may beindependent of it.

Various options are available for handling of the build table 512. Forexample, when the build table 512 has been advanced through severalcycles and reached a limit of how far it can be advanced through theapparatus 510, it could be removed, cleaned or otherwise rejuvenated,and replaced back into the apparatus 510 for further use. Alternatively,a plurality of build tables 512 could be provided. When each build table512 is completely used, it could be removed and replaced with a cleanbuild table 512. The used build tables could then be cleaned orotherwise rejuvenated and placed back into rotation for further use.

Alternatively, when the build table has reached a limit of how far itcan be advanced through the apparatus 510, the material applicator 516and the material remover 520 could be disengaged and the build table 512could be moved in a reverse direction to reset it back to an initialposition, readying it for further use.

The method and apparatus described herein has several advantages overthe prior art. In particular, it eliminates a major pathway for buildfailures in vat-based photopolymerization. It also potentially has lowercost, less material waste, and higher process speed compared to priorart tape casting methods.

The foregoing has described a method and apparatus for additivemanufacturing. All of the features disclosed in this specification(including any accompanying claims, abstract and drawings), and/or allof the steps of any method or process so disclosed, may be combined inany combination, except combinations where at least some of suchfeatures and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanyingclaims, abstract and drawings) may be replaced by alternative featuresserving the same, equivalent or similar purpose, unless expressly statedotherwise. Thus, unless expressly stated otherwise, each featuredisclosed is one example only of a generic series of equivalent orsimilar features.

The invention is not restricted to the details of the foregoingembodiment(s). The invention extends to any novel one, or any novelcombination, of the features disclosed in this specification (includingany accompanying claims, abstract and drawings), or to any novel one, orany novel combination, of the steps of any method or process sodisclosed.

What is claimed is:
 1. An additive manufacturing apparatus, comprising:a build table, at least a portion of which is transparent, the buildtable defining a build surface; a material applicator operable todeposit a radio-energy-curable resin on the build surface; a stagepositioned facing the build surface of the build table and configured tohold a stacked arrangement of one or more cured layers of the resin; oneor more actuators operable to change the relative positions of the buildtable and the stage; a radiant energy apparatus positioned adjacent tothe build table opposite to the stage, and operable to generate andproject radiant energy on the resin through the build table in apredetermined pattern; a drive mechanism operable to move the buildtable so as to expose a new portion thereof for each layer; and amaterial remover operable to remove remnants from the build surface. 2.The apparatus of claim 1 wherein: the build table is mounted forrotation about a central axis; and the drive mechanism is configured toselectively rotate the build table about the central axis.
 3. Theapparatus of claim 1 wherein the drive mechanism is configured toproduce movement of the build table along an open path.
 4. The apparatusof claim 1 wherein the material applicator is configured for operationwhich is physically linked to movement of the build table.
 5. Theapparatus of claim 1 wherein the material remover is configured foroperation physically linked to movement of the build table.
 6. Theapparatus of claim 1 wherein a trough for collecting excess resin ispositioned adjacent the build table.
 7. The apparatus of claim 6 furthercomprising a material circulating apparatus operable to move uncuredresin from the trough to the material applicator.
 8. The apparatus ofclaim 1 where the material applicator is configured to selectivelydeposit more than one resin.
 9. The apparatus of claim 1 wherein thebuild surface includes a non-stick coating.
 10. The apparatus of claim 1wherein at least a portion of the build surface is oxygen-permeable. 11.An additive manufacturing apparatus, comprising: a build table mountedfor rotation about a central axis, wherein at least a portion of thebuild table is transparent, and the build table defines a build surface;a drive mechanism configured to selectively rotate the build table aboutthe central axis; a material applicator operable to deposit aradio-energy-curable resin on the build surface; a stage positionedfacing the build surface of the build table and configured to hold astacked arrangement of one or more cured layers of the resin; one ormore actuators operable to change the relative positions of the buildtable and the stage; a radiant energy apparatus positioned adjacent tothe build table opposite to the stage, and operable to generate andproject radiant energy on the resin through the build table in apredetermined pattern; and a material remover operable to removeremnants from the build surface.
 12. The apparatus of claim 11 whereinthe build table is circular or ring-shaped.
 13. The apparatus of claim11 wherein the material applicator is configured for operation which isphysically linked to movement of the build table.
 14. The apparatus ofclaim 13 wherein the material applicator comprises a recoater operableto level a layer of the resin.
 15. The apparatus of claim 11 wherein thematerial remover is configured for operation physically linked tomovement of the build table.
 16. The apparatus of claim 15 wherein thematerial remover comprises a scraper positioned to engage the buildsurface.